The invention relates generally to internal combustion engines, and more particularly to air-cooled rotary internal combustion engines.
Rotary internal combustion engines, or rotary engines, are attractive because of their high theoretical efficiency and simplicity of construction and operation. Their relatively high power output and compact size make them particularly attractive for utilization in applications in which size and weight are prime considerations.
In the applicant's U.S. Pat. No. 3,865,086, issued Feb. 11, 1975, an improved and simplified rotary internal combustion engine is disclosed in which the power of internal combustion is converted to a lever force acting upon an output axis by means of levers revolving about a second axis which is displaced from the output axis, thus permitting the direct application of torque to the output axis. The disclosure of this patent is fully incorporated herein by reference.
The compact size and lightweight of the rotary engine can be further enhanced by the use of air-cooling in place of the bulkier and heavier closed, recirculating coolant system. Air-cooling of internal combustion engines is known in the art. For example, in U.S. Pat. No. 2,209,996, issued Aug. 6, 1940 to A. H. Neuland, an internal combustion engine is provided with a fan and cooling ducts to direct air flow over the piston, spark plugs and oil cooler, and to mix the cooling air with the exhaust gases before the mixture is discharged from the engine. Other examples of air-cooled internal combustion engines are disclosed in U.S. Pat. Nos. 1,485,591, 2,020,089, 2,288,018, 2,369,002 and 3,911,876.
The problem of short service life of the sealing elements in a rotary engine, particularly the tip or apex sealing elements provided between the rotor and the rotor chamber, has received considerable attention recently. Factors which contribute to the short life of the apex seal include high rotational speed of the rotor, the high friction associated with this high speed, and the requirement to provide continuous and effective fluid seal as the seal is rotating. In addition to the requirement for sealing between the tips of the rotor and the rotor housing, the rotary engine also requires sealing between the sides of the rotor and the rotor chamber, which is usually provided by the side seals.
Many different solutions have been proposed for the problem associated with the tip or apex seals. For example, one type of such seal includes a sealing blade or element which is pivotally carried on the rotor, and is biased into sealing contact with the rotor chamber by the force of the combustion gases. This type of sealing offers the advantage that as the pressure of the gases increases, the amount of sealing force provided increases proportionally. Examples of such sealing elements may be found in U.S. Pat. Nos. 1,004,776, 1,406,140 and 3,891,359. The requirement for providing a fluid seal between the sides of the rotor and the sides of the rotor chamber have not been as critical and have generally been met by the provision of annular fluid seals in the walls of the rotor chamber.